Piriformis Muscles Syndrome

Introduction

Characterized by extrapelvic sciatic nerve compression
- sometimes called deep gluteal syndrome
Pathoanatomy
- sciatic nerve entrapment occurs
  - anterior to piriformis muscle or posterior to obturator internus/gemelli complex
  - at level of ischial tuberosity
Associated conditions
- may be related to anatomic anomalies including
  - bipartite piriformis
  - variations of sciatic nerve path
  - tumors
  - aneurysm of inferior gluteal artery

Anatomy

Piriformis muscle
Sciatic nerve

Presentation

Symptoms
- nonspecific and include pain in the posterior gluteal region and migrating down the back of the leg
- pain may be burning or aching in nature similar to sciatica symptoms
  - but not due to lower back pain
Physical exam
- FAIR test (flexion, adduction, and internal Rotation of hip) can reproduce symptoms
  - maneuver places piriformis muscle on tension

Imaging

Radiographs
- unremarkable
MRI
- usually unremarkable
- lumbar MRI helpful to rule out spine as cause of compression of sciatic nerve
Electrodiagnostic studies
- can document functional impairment of sciatic nerve

Treatment

Nonoperative
- rest, NSAIDS, muscle relaxants, PT, steroid injections
  - indications
    - first line of treatment
  - technique
    - focused on stretching the piriformis muscle and short external rotators
    - corticosteroid injection directed near the piriformis muscles
Operative
- piriformis muscle release and external sciatic neurolysis
  - indications
    - only indicated in refractory cases after failed conservative measures

TAG

(OBQ09.37) Which of the following is the most common anatomical pattern of the sciatic nerve as it exits the pelvis? Topic

Review Topic

1. As a single nerve, anterior to the piriformis muscle
2. As a single nerve, posterior to the piriformis muscle
3. As two branches, both anterior to piriformis muscle
4. As two branches, one anterior to piriformis and one through the piriformis muscle
5. As two branches, both posterior to the piriformis muscle

PREFERRED RESPONSE ▶

DISCUSSION: The most common anatomical pattern is a single sciatic nerve which passes anterior to the piriformis muscle, however it is important to note that there are other common anatomical variants.

Pokorny et al in a study of 91 cadavers found atypical anatomy of the sciatic nerve in almost 21% of cases. The normal anatomy seen in 79% is a single sciatic nerve exiting underneath (passing anterior) to the piriformis. The most common variant, seen in 14%, is the sciatic nerve splitting proximal to the piriformis with one branch passing anterior to and one branch passing through the piriformis.

Illustration A is an anatomic drawing of the sciatic nerve passing anterior to the piriformis.

Illustrations: A

REFERENCES:

1. Pokorný D, Jahoda D, Veigl D, Pinskerová V, Sosna A. Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty. Surg Radiol Anat. 2006 Mar;28(1):88-91. Epub 2005 Nov 26. PMID:16311716 (Link to Abstract)

2. Tornetta P III: Hip dislocations and fractures of the femoral head, in Bucholz RW, Heckman JD (eds): Rockwood and Green’s Fractures in Adults, ed 5. Philadelphia, PA, Lippincott Williams & Wilkins, 2001, p 1556

Question Authors:

Ben Taylor MD, Ben Taylor MD, Patrick McCulloch MD,

Please Rate Educational Value!

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Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Pokorný D, Jahoda D, Veigl D, Pinskerová V, Sosna A. Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty. Surg Radiol Anat. 2006 Mar;28(1):88-91. Epub 2005 Nov 26. PMID:16311716 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Tornetta P III: Hip dislocations and fractures of the femoral head, in Bucholz RW, Heckman JD (eds): Rockwood and Green’s Fractures in Adults, ed 5. Philadelphia, PA, Lippincott Williams & Wilkins, 2001, p 1556

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